Low-grade fibromyxoid sarcoma incidentally discovered as an asymptomatic mediastinal mass: a case report and review of the literature

Non-IgG4-Related Fibrosing Mediastinitis Diagnosed on Core Needle Biopsy and Treated with Steroids: A Case Study and Review of the Differential Diagnoses

OBJECTIVES

This study aimed to investigate the histological characteristics and treatment efficacy of non-immunoglobulin G4-related fibrosing mediastinitis and discuss differential diagnoses for this rare entity.

METHODS

We present a case study of non-immunoglobulin G4-related fibrosing mediastinitis diagnosed on core biopsy and treated with steroids. A total of four 18-gauge core needle biopsy specimens were obtained for surgical pathology. Analysis of the patient's medical history, radiological characteristics of fibrosing mediastinitis, histological features, immunohistochemistry results, the differential diagnosis and treatment efficacy of different types of fibrosing mediastinitis was performed.

RESULTS

This report describes a unique presentation of fibrosing mediastinitis (syncope and weight loss) that was concerning for malignancy. Histological, laboratory and radiographical studies confirmed the diagnosis of non-immunoglobulin G4-related fibrosing mediastinitis. The patient received corticosteroid treatment which showed marked improvement after 1 month of treatment.

CONCLUSIONS

Fibrosing mediastinitis is an extremely uncommon entity with unknown pathogenesis, and it is more important to rule out malignancy and infection than to delineate between fibrosing mediastinitis and IgG4-related disease. In doing this, we may reasonably initiate a trial of corticosteroids which may prove beneficial, as in this patient. More studies on the pathogenesis of fibrosing mediastinitis are necessary to guide better directed treatments.

Novel KMT2B gene mutation in MUC4 positive low-grade fibromyxoid sarcoma

BACKGROUND

Low-grade Fibromyxoid Sarcoma(LGFM)is a rare fibrosarcoma, which mainly occurs in young people and is mostly seen in the trunk and limbs. The tumor is usually FUS-CREB3L2 fusion caused by t(7;16)(q32-34;p11)chromosome translocation, and rarely FUS-CREB3L1 and EWSR1-CREB3L1 fusion. MUC4 diffuse strong positive can be used as a specific index of LGFM. LGFM is similar to Sclerosing Epithelioid Fibrosarcoma(SEF) and may have the same origin.

CASE PRESENTATION

We report a case of LGFM in the chest wall. A female who is 59 years old. In 2016, CT showed dense nodule shadow and focal thickening of the left pleura, the patient underwent surgery, Pathological report that low to moderate malignant fibrosarcoma(fibromyxoid type). The CT re-examination in 2021 showed that the tumors on the left chest wall were significantly larger than before. Pathological examination showed the disease is composed of alternating collagen like and mucinous areas. Under high-power microscope, the tumor cells are consistent in shape, spindle or short spindle, and the tumor cells are arranged in bundles. In local areas, the density of tumor cells is significantly increased, mixed with collagen fibers, and small focal SEF appear. The result of immunohistochemistry showed that SMA, Desmin, CD34, STAT6, S100, SOX10, HMB45 and Melan A were negative, EMA was weakly positive, MUC4 was diffuse and strongly positive, and Ki67 index was low (3%).

CONCLUSION

Sequencing results showed that MET, EGFR, KMT2B and RET gene were mutated in LGFM, and KMT2B gene had cancer promoting effect, but there was no literature report in LGFM, which may be of certain significance for the diagnosis and treatment of LGFM.

Case report: Primary pleural low-grade fibromyxoid sarcoma in a 4-year-old boy with molecular confirmation

Low-grade fibromyxoid sarcoma (LGFMS) is a rare malignant fibroblastic tumor, principally affecting the deep tissues of the proximal trunk and extremities in young adults. However, primary pleural LGFMS is extremely rare, and only three cases have been reported in the previous English literature without genetic confirmation. Furthermore, the historical pleural LGFMS cases were all adults, and the primary pleural LGFMS in children has never been reported to date. Here, we presented a primary pleural LGFMS in a 4-year-old boy with detailed clinical, pathological, and molecular results. Histologically, the current tumor showed typical alternating collagenous and myxoid areas, containing spindled or oval tumor cells arranged in a whorled and short fascicular pattern. In some areas, the tumor cells exhibited moderate atypia, and mitotic figures were identified but without the identification of giant collagen rosettes. Immunohistochemically, all the neoplastic cells showed strong and diffuse positivity for MUC4. Genetically, FUS gene rearrangement was revealed by fluorescence in-situ hybridization (FISH), and subsequently, next-generation sequencing (NGS) and polymerase chain reaction (PCR) further demonstrated the FUS::CREB3L2 fusion transcript. To the best of our knowledge, this is the first case of primary pleural LGFMS with the identification of FUS gene rearrangement and FUS::CREB3L2 fusion in a 4-year-old child. Our study expands the age range of pleural LGFMS and highlights the combination of morphological, immunohistochemical, and molecular analyses in such challenging cases.

Low-grade fibromyxoid sarcoma arising in the mediastinum: Case report and review of the literature

Low-grade fibromyxoid sarcoma (LGFMS) is a rare tumor characterized by bland histological features and aggressive clinical course, it is a distinctive variant of fibrosarcoma with high metastasizing potential and sometimes a long interval between tumor presentation and metastasis, the most common anatomic locations of occurrence are the lower extremities, thorax, inguinal area, and upper limbs, Here, we present the case of a 29-year-old patient with a deceptively benign-appearing mass arising in the mediastinum that had been discovered on computed tomography, a biopsy under cervicotomy was performed and histopathological examination revealed low-grade fibromyxoid sarcoma. In conclusion, LGFMS can arise in the mediastinum, and physicians should consider this entity as a differential diagnosis in the presence of such mass.

Case report and review of literature: Resection of a huge mediastinal low-grade fibromyxoid sarcoma with neck, axillary, and lung involvement

Low-grade fibromyxoid sarcoma is an extremely rare malignant neoplasm, with an incidence of 0.18 per million, and comprises 0.6% of all soft tissue sarcomas. It has a high recurrence rate and late metastatic spread and is chemotherapy and radiotherapy insensitive. This paper reports a case of an unusually large mediastinal low-grade fibromyxoid sarcoma in a 55-year-old patient. The tumor was engulfing the main blood vessels of the mediastinum, involving the lung, and extending beyond the chest cavity to involve the cervical and axillary regions. The patient has a 21-year history of frequent surgical resections for lesions that were repeatedly misdiagnosed as neurofibroma. The tumor was successfully resected by a challenging operation that involved mediastinal mass resection, chest wall mass resection, and wedge resection of the left upper lobe of the lung. The deceivingly benign-looking histology of this tumor makes it a commonly misdiagnosed one, requiring careful assessment by pathologists to reach the right diagnosis. Surgical resection with clear margins remains the treatment of choice for these lesions. Due to the behavior of this tumor, once detected and managed, extensive long-term follow-up is always recommended.

Mediastinal Low-Grade Fibromyxoid Sarcoma With FUS-CREB3L2 Gene Fusion

Low-grade fibromyxoid sarcoma (LGFMS) is a rare subclass of sarcoma. Histologically, they are characterized by bland-appearing fibroblastic spindle cells and are similar to sclerosing epithelioid fibrosarcoma (SEF) subtype. The standard treatment of this aggressive tumor subtype is surgical removal with wide excision in conjunction with doxorubicin chemotherapy. Due to the rarity of this disease, effective systemic therapies are lacking and patient outcomes remain poor. Herein, we report on a 50-year-old male who presented with severe shortness of breath. Subsequent imaging revealed pericardial effusion and large mediastinal mass consistent with locally advanced disease. Fine needle biopsy demonstrated malignant, Ewing-like round tumor cells. Further genetic analysis affirmed the presence of FUS-CREB3L2 gene fusion. The patient was treated with doxorubicin and survival time from the initial presentation was five months. To date, there are limited reports of this disease. Few targeted therapies or immunotherapies for LGFMS exist, and a dire need for new therapy development remains.